Did you know that waterproofing is just 1.8% of construction cost, but a lack of waterproofing is responsible for 83% of building defect complaints?

For both hob or step-down showers if leaking is a major problem, treat the project ‘as new construction’, pull out the existing shower and start again. However, for minor repairs, pull out any silicon and replace joint sealing with polyurethane. Limit the water penetration by applying a water repellent over the tile grout lines and tiles. Ensure the exit drain is waterproofed. In more extreme cases cover tiles and use a trafficable polyurethane floor.
Australian Institute of Waterproofing